Jun 4, 2025
Type 1 CAMT
Type 2 CAMT
Clinical Features
Laboratory Findings
Diagnosis and Complications
Learning Points: CAMT Vs Immune Thrombocytopenia
It tends to show an autosomal recessive inheritance. The gene involved is the MPL gene, a gene which codes for TPO receptors. TPO is essential for megakaryocytic proliferation. They eventually give rise to platelets. TPO receptor is also needed for maturation and preventing apoptosis in the other hematopoietic stem cells. As the age advances, there is increased apoptosis happening of the erythroid and the myeloid cells.
There are basically two types of CAMT
Type 1 CAMT and type 2 CAMT
More severe form
Caused by nonsense mutation in the mpl gene due to this no functional TPO receptor is formed. They tend to have severe thrombocytopenia in infancy, and they tend to develop pancytopenia very early (within 3-4 years of onset of thrombocytopenia).
Less severe. Caused due to missense mutation happening in the MPL gene. They will have thrombocytopenia but a mild and relatively less dramatic course.
There will always be in the neonatal period, these children will have thrombocytopenia. It will manifest in the form of petechiae, purpura, epistaxis. As the age advances, in the first decade of life, they all develop pancytopenia. Also, the features of anemia and recurrent infection due to leukopenia. Some patients of type 2 CAMT, tend to develop a slight elevation in platelet count beyond infancy. It does not affect the likelihood of progression to pancytopenia but this is a change that can be seen in the patients.
In 20% cases of CAMT other congenital anomalies, basically involving 2 organ systems CNS and the cardiovascular system. In CNS, cerebellar and cerebral hypoplasia is found and they will also have delayed milestones. In the cardiovascular system, there is an increased risk of congenital heart disease VSD, ASD, PDA, and Coarctation of Aorta.
The platelet count will be low and in patients with one pancytopenia there will fall in the Hb and TLC. In addition, they will have elevation in HbF and macrocytosis, and macrocytic RBCs. BM will show, there is a severe reduction in the megakaryocytes in all individuals. Those with pancytopenia will also have a reduction in other hematopoietic lineages.
In CAMT, on platelet transfusion, there is an adequate response to it. There is improvement in bleeding manifestation till the time circulating platelets are sufficient in the circulation. There will be no response to corticosteroids. In Immune thrombocytopenia, Platelets transfusion will show inadequate or no response. There will be a response to corticosteroids.
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